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Researchers worldwide are studying thermal energy storage with phase change materials because of their substantial benefits in the enhancement of energy efficiency of thermal drying systems. A two-stage convectivevacuum impulsive drying plant is a technology for the manufacturing of chemical and food products with high quality and low energy costs. Energy consumption during the drying process is the main indicator in terms of economy. In this paper, a brief and focused review of the peculiarities of TEAs with PPCMs and opportunities of their application in such drying systems is done and discussed. The paper described the mentioned manufacturing system. The advantages of paraffin wax and thermal conductivity improvement techniques were demonstrated for their use as heat storage materials in CVID drying units. The results of similar previous studies were presented. The results of the experimental studies conducted by the researchers proved that the use of heat accumulators with PCMs increased the overall energy efficiency of drying systems. Finally, integration of TEAs based on modified PPCMs in the CVID system was recommended to intensify thermal energy, reduce thermal influence on the main indicators of the vacuum pump during the evacuation process, and decrease production costs. [ABSTRACT FROM AUTHOR]

The present work studies the convective drying of a granular porous medium in a bed of olive pomace. The experimental tests were conducted in a closed convection drying loop of hot air. The experimental tests measured the mass loss over time. Tests were carried out for five temperature values: 60 ± 0.1 °C, 70 ± 0.1 °C, 80 ± 0.1 °C, 90 ± 0.1 °C and 100 ± 0.1 °C, respectively. Moreover, three values of velocities of the drying air, 1 ± 0.01 ms−1, 1.5 ± 0.01 ms−1 and 2 ± 0.01 ms−1, were considered. The effects of initial humidity, bed thickness and pomace composition on the drying process were studied. The results show that the moisture content decreases when the temperature and the velocity of the drying air increase. In addition, the composition of olive pomace (pulp, pits and raw pomace) significantly affects the drying time. A characteristic drying curve and its equation were determined. Seven thin layer drying models were tested, and the Midilli et al.'s model produced the best agreement. The effective moisture diffusivity coefficient (Deff), the activation energy (Ea) and the pre-exponential coefficient of the Arrhenius law were evaluated. The results could be of great help for the pretreatment of crude olive pomace when moving to industrial scale and before passing to the step of biofuel (pellets, briquettes or logs, Syngas) production. [ABSTRACT FROM AUTHOR]

This study aims to comprehensively investigate the effects of hot-air dehydration on the quality of blue honeysuckle berries (Lonicera caerulea L.). The results demonstrated that drying with hot air at 40–65 °C for 7–72 h resulted in blue honeysuckle berries with a moisture content of 0.21–1.10 g H2O/g dry weight. Generally, low to medium temperatures (40–55 °C) showed a better effect on the quality than high temperatures (60–65 °C). Specifically, drying at 40 °C exclusively resulted in better retention of cuticular wax, the best sensory appearance, and the highest total phenolic content. Drying at 45 °C and 50 °C resulted in the highest antioxidant capacity and the optimal sensory flavor. Drying at 55 °C led to the highest soluble solid/acid ratio, ascorbic acid concentration, total flavonoid, and total anthocyanin. The work introduces an innovative raw berry product and provides a comprehensive practical and theoretical framework for convective dehydration of blue honeysuckle berries.

This study aimed to evaluate the effect of convective and microwave drying on the bioactive-compounds content of blackberry (Rubus fruticosus) fruits, as well as drying parameters and energy consumption. The fruit was dehydrated in a convective dehydrator at a temperature of 50 °C and 70 °C and in a microwave oven at power levels of 90 W, 180 W and 240 W. The highest amount of anthocyanins, polyphenols and antioxidant capacity were obtained in blackberry fruits that were microwave dried at 90 W and 180 W (46.3–52.5 and 51.8–83.5 mg 100 g−1 dm of total anthocyanins, 296.3–255.8 and 418.4–502.2 mg 100 g−1 dm of total phenolics, and 1.20–1.51 and 1.45–2.35 mmol TE 100 g−1 dm of antioxidant capacity for 90 W and 180 W models, respectively). It turned out that microwave dehydration shortened the processing time and lowered the energy consumption compared to convective drying (a significantly reduced drying time of 92–99% with microwave dehydration). Blackberry fruits dehydrated at 240 W showed the shortest dehydration time (59–67 min), minimal energy consumption (0.23 kWh) and the most efficient diffusion (1.48–1.66 × 10−8 m2 s−1).

The present study focused on evaluating the biochemical profiles of four apricot cultivars (cv.) (Prunus armeniaca L.) grown in Latvia and demonstrating their processing to obtain the food product, dried candied fruit (DCF). The fingerprinting of apricot fruit approached by LC-MS and ultraviolet–visible spectroscopy revealed the abundance of bioactives responsible for the antioxidant activity. The outstanding composition of group compounds, i.e., phenolics, flavonoids, and vitamin C, was observed in the cv. ‘Dimaija’, followed by cv. ‘Gundega’ and cv. ‘Velta’. The lowest values were found in the cv. ‘Boriss’ and fruit from a market of Greek origin. However, the latter two contained the highest carotenoid levels due to a more pronounced maturity. Amongst the 13 individual phenolics detected, rutin, chlorogenic and neochlorogenic acids, catechin, and epicatechin prevailed. The concentrations observed were the highest in cv. ‘Dimaija’, followed by cv. ‘Velta’ and cv. ‘Gundega’. Osmotic dehydration and convective drying of apricot fruit variedly influenced the content of bioactives in DCF products. The most substantial decrease due to thermal lability was observed in the vitamin C content in DCF, accounting for a 95.3% loss for all cultivars. The content of total phenolics, flavonoids, and carotenoids in DCF, on average, was 62.7%, 49.6%, and 87.6% lower than that observed in the raw fruit, respectively. On average, the content of individual phenolics in DCF, such as rutin and chlorogenic acid, decreased by 63.8% and 20.8%, respectively. The decline in the content of bioactives was conditioned by the physical migration of the cell components to the hypertonic solution. However, the increase in the content of cell wall-bound phytochemicals, such as catechin and epicatechin, after osmotic dehydration and convective drying, was observed in DCF, corresponding to a 59.5% and 255.64% increase compared with the raw fruit, respectively. Panelists generally responded positively to the developed DCF; however, greater preference was given to products with a lower phenolic content, such as cv. ‘Boriss’ and those produced from the market fruit. It is believed that the high flavan-3-ols content, along with chlorogenic acid, contributed to the bitter taste of DCF. Overall, apricot fruits represent the abundance of bioactives retained in DCF after osmotic dehydration and convective drying. The findings observed in the current study allow to consider DCF as a functional food; however, given the high sugar content, their consumption should be in moderation.

The kinetics of drying dense wool fabric in different regimes has been studied experimentally. The mass-conducting (diffusion) properties of the fabric are determined depending on the content of moisture in it and its temperature. For the convenience of engineering calculations, the obtained data on the mass conductivity of the fabric are approximated by its dependences on moisture content and temperature. It has been established that the kinetics of convective drying of a dense wool fabric is adequately described by A. V. Luikov's model of heat and moisture transfer subject to the dependence of the mass conductivity of the fabric on its moisture content and the temperature of the drying agent. The proposed approach to the calculation of the kinetics of drying a dense wool fabric, its moisture content, and its temperature can be used in the design of the processes of drying various fabrics. [ABSTRACT FROM AUTHOR]

A numerical study (conjugate modeling) of potato cuboid separation in convective drying is performed with the Large Eddy Simulation approach. Any in-line potato array is represented by a single interacted zone through periodic boundary conditions. Numerical code is validated with four experimental studies focused on hydrodynamics (two cases), heat transfer (one case), and mass transfer (one case). Twelve case studies have been proposed to study the effect of streamwise and spanwise distances on heat and mass transfer. Results show that low streamwise separations (0.25) strongly affect the potato drying by the presence of a quasi-stationary wake that causes a blocking effect. The potato cuboid's best thermal uniformity and mass transfer are presented at a spanwise distance (0.75) and streamwise separations (1.0). Results can be applied to get uniform heat and mass transfer in drying chambers. [ABSTRACT FROM AUTHOR]

Kaolin clay is one of the essential components of utility and technical ceramic products. Drying is one of the stages of its production and is crucial for the quality of the obtained products. Due to the low energy efficiency of the dryers, it is also one of the most energy-intensive operations performed not only in the production of ceramics but in the industry as a whole. For this reason, modern drying techniques are sought. They are required to be energy efficient, sustainable and produce high-quality products. An example is the so-called hybrid drying, which combines several drying techniques (energy sources) into one process. The aim of this work was to determine the impact of microwave and infrared radiation on the kinetics and energy consumption of convective drying of kaolin clay and the quality of the products. The interaction of convective, microwave and infrared drying was investigated. Drying times, energy consumption and visual quality were compared for the tested processes. The fastest process was convection–microwave drying, where a reduction in drying time of 70% and energy consumption of 50% was observed. Unfortunately, intensive drying had a negative impact on the quality of the products (numerous cracks on the side surface). The best drying methods are those that use all energy sources simultaneously and periodically. Hybrid processes that use all energy sources in a periodic manner had the greatest efficiency. The drying time in these programs was shortened in relation solely to the convection process by 45 to 50% while reducing energy consumption by 3–18%. The product had the best quality. [ABSTRACT FROM AUTHOR]

The study examined the effects of pulsed electric field treatment on the kinetics and properties of convective-dried mushrooms using different drying agents. Increasing the drying air temperature reduced drying time, while the use of dehumidified air resulted in faster water removal. PEF treatment, depending on the parameters, shortened the drying time maximum by 12% or extended the drying time. The physical (dry matter content, rehydration properties, hygroscopic properties, and color) and chemical (polyphenols content and anti-oxidant activity) properties were analyzed. The dry matter contents of the mushrooms were influenced by the drying temperature, while PEF pre-treatment did not influence the rehydration and hygroscopic properties in both cases of drying using air humidity. However, the color parameters were affected by the drying method and energy input, with higher energy input leading to decreased lightness, increased redness, and color saturation. The chemical analyses revealed that the anti-oxidant compounds in the dried mushrooms were influenced by various factors, with PEF treatment and drying non-dehumidified air polyphenol content increasing, whereas dehumidified air caused more phenolic degradation if it was combined with PEF treatment. Anti-oxidant activity varied depending on the drying agent, with non-dehumidified air generally exhibiting better properties. The highest total polyphenol content and best anti-oxidant properties were obtained for the PEF pre-treated with 3 kJ/kg of energy and dried with non-dehumidified air at a temperature of 70 °C. [ABSTRACT FROM AUTHOR]

Drying of a deformable saturated porous medium based on convective tempering is a novel method that can enhance energy efficiency and the quality of the dried product itself. In this experimental investigation, the performances of this specific technique are compared with those of a standard stationary drying process in terms of deformation, drying kinetics, moisture redistribution, and energy consumption. In particular, the response of a deformable saturated porous medium (Kaolin) is considered. The results are critically discussed pointing out advantages and drawbacks. [ABSTRACT FROM AUTHOR]

The rehydration behavior at 100 ± 2 °C with a solid:liquid ratio (m/m) of 1:100 for pumpkin cubes dehydrated by convective drying was determined by the Peleg model. The rehydration of the pumpkin cubes dehydrated by convection at 50, 60 and 70 °C had a good fit to the Peleg model, with the pumpkin cubes dried at 60 °C presenting the best fit. The volume of the dice increased over the rehydration time until it recovered its initial volume of 1 cm³. [ABSTRACT FROM AUTHOR]

In order to optimize the convective drying process parameters of peanuts and to provide a theoretical basis for the scientific use of energy in the drying process, this study took single-particle peanuts as the research object and analyzed the heat and mass transfer process during convective drying. In addition, a 3D two-component moisture heat transfer model for peanuts was constructed based on the mass balance and heat balance theorem. Moreover, the changes in the internal temperature and concentration fields of peanut pods during the whole drying process were investigated by simulations using COMSOL Multiphysics. The model was validated by thin-layer drying experiments, compared with the one-component model, and combined with low-field NMR technology to further analyze the internal moisture distribution state of peanut kernel drying process. The results show that both models can effectively simulate the peanut thin-layer drying process, and consistency is found between the experimental and simulated values, with the maximum errors of 10.25%, 9.10%, and 7.60% between the simulated moisture content and the experimental values for the two-component model, peanut shell, and peanut kernel models, respectively. Free water and part of the weakly bound water was the main water lost by peanuts during the drying process, the change in oil content was small, and the bound water content was basically unchanged. The results of the study provide a theoretical basis to accurately predict the moisture content within different components of peanuts and reveal the mechanism of moisture and heat migration during the drying process of peanut pods. [ABSTRACT FROM AUTHOR]

As a section on improving the energy efficiency and thermal efficiency of convection dryers, a different airflow distribution system in the convection dryer was established. The grape drying experiment was investigated by applying three types of distribution air inside a convection hot-air dryer. The vertical system (VS) in which hot air passes vertically through the tray of samples. However, the air was delivered parallel to the sample tray in two horizontal systems (HS) Types (I, II). The investigations were approved with the different air-drying temperatures of 40, 50, and 60 °C at different velocity 1.0, 1.5, and 2.0 m/s. The drying time in the horizontal dryer compared to the vertical system was significantly less. The data analysis showed that horizontal energy consumption with a type (II) dryer was low while the energy consumption was high under the vertical dryer. Moreover, applying the horizontal Type (II) for grapes drying had numerous improvements above the conventional vertical system, such as shorter processing times, less overall energy utilisation, and higher dryer thermal efficiency. According to the results, after fitting the experimental data with eleven drying kinetics models and comparing the results in terms of the root mean square error (RMSE), the reduced chi-square (χ2), and the correlation coefficient (R2), it was obtained that logarithmic model can give practically accurate evaluations of the drying curve for grapes drying in different convection dryers.

Green asparagus is widely consumed fresh due to its high nutritional value and a low calorie content. However, its short shelf-life due to a high water content causes high postharvest losses. In this study, we aimed to develop an innovative asparagus herbal drink to ease postharvest losses and diversify asparagus-derived products. We investigated the effects of process parameters on the quality of the herbal drink from green asparagus. In particular, we determined the optimal length and grinding size for asparagus and selected suitable blanching and drying methods. Analytical responses included the contents of total soluble solids, polyphenol, carbohydrates, and vitamin C, as well as the visual appearance of asparagus samples. The length of 5 mm was found suitable for subsequent steps as it facilitated an increase in solute in the asparagus infusion. Microwave blanching and convective drying were selected to achieve high contents of total soluble solids, polyphenol, carbohydrates, and vitamin C in the asparagus infusion. Dried asparagus ground into 1.5–2.0 mm particles was packaged into tea bags. The asparagus infusion subjected to sensory evaluation had a yellowish color, a characteristic asparagus flavor, and a relatively sweet taste. Total soluble solids in the infusion amounted to 26%. Our results showed a possibility of developing an asparagus herbal drink which could be a potent product in the commercial market. Therefore, further large-scale studies of the asparagus herbal drink should be carried out to enhance its feasibility in the food industry.

Solar collectors are thermal devices that can trap solar energy and convert it to heat. This heat can be used for different industrial applications, for example, the drying of food is one of the most useful applications of solar collectors. This work aims to design and build a solar collector using nanofluids for the convective drying of food. The dimensions of the solar collector were 1 m2 by 20 cm with an angle of inclination of 45°. The collector was composed of 9-mm thick tempered glass and a heat exchanger in which the nanofluids circulate. Nanofluids were designed based on canola oil and nanopowders (>50 nm) of Al2O3, CuO, and a 1:1 (w/w) mixture of both. Thermal profiles were determined using differential scanning calorimetry (DSC). The solar collector temperatures were recorded using an Agricos® unit. The maximum temperatures of the air leaving the collector were 39.1°C, 44°C, 54°C, and 47.1°C for canola oil, and the nanofluids composed of Al2O3, CuO, and the 1:1 mixture, respectively, with a maximum efficiency of 65.09%. An increase in the outlet air temperature was observed using the nanofluids compared to canola oil alone

The object of research is the process of convective and combined drying of apple raw materials treated before dehydration in an ultrasonic bath. The use of pretreatment solves the issue of intensifying the dehydration process and maintaining the quality of the product. Sonication for 5 min reduces the dehydration process by 13.7 %, and at 10 min processing – by 27.8 % compared to traditional convective drying. With increasing processing time to 20 minutes, the dehydration rate deteriorates. Sonication of raw materials for 5 minutes under combined heating does not intensify the dehydration process, and within 10 and 20 minutes it reduces the efficiency of moisture removal. When processed for 10 minutes, the time to reach the final moisture content is increased by 17.2 %, and at 20 min – by 23.4 % compared to control samples. Regardless of the processing time, there is a decrease in the maximum temperature of the samples in the combined drying process. When processed for 5 minutes, the maximum temperature of the samples decreased by 4.3 %, and with 10 and 20-minute processing – by 8.6 % and 12 % compared to the temperature of samples without sonication. The results are explained by the "sponge effect" caused by ultrasonic vibrations and the phenomenon of cavitation that occurs in the liquid during the action of the ultrasonic field. The peculiarity of the pre-sonication before drying is the possibility to intensify the convective dehydration process without increasing the heat carrier's temperature. The use of this type of processing in a combined energy supply will solve the problem of preserving the quality of the finished product by reducing the maximum temperature of the raw material. The research reported here could be a prerequisite for practial design of an energy-efficient electrical system for drying fruit and vegetable raw materials. [ABSTRACT FROM AUTHOR]

Comprehensive studies into the influence of various types of preliminary preparation of blueberry berries for drying have established the amount of wax coating, color, and the total duration of dehydration of raw materials. A comparison of 2 types of preliminary preparation was made: hygrothermal treatment and infrared radiation treatment directly during drying. It was established that after treatment with infrared radiation, 53 times more wax plaque came off the berries than after hygrothermal treatment. Microscopic studies of sections of the parenchymal part of berries recorded the state of the cell membranes and the color of the raw materials without prior processing, with pretreatment, and after drying. It was found that berries dried without pretreatment (mode parameters of heat carrier: t=70 °C, v=2 m/s, d=10 g/kg dry air. Win=85 %, c W = 9, 3 % ) have partially destroyed cell membranes but the color of the dried material is preserved to the maximum. It was observed that the berries after hygrothermal treatment have partially destroyed parts of the cell membrane, which makes it possible to more intensively release moisture from the material after drying, the maximum color of the product is also preserved. In berries, after treatment with infrared radiation of 100 W for 10 minutes, the cells remain convex with partial destruction of the shell of some cells but, after pretreatment, the intensity of color decreases. Studies into the kinetics of drying blueberry berries have confirmed that the use of infrared radiation with a capacity of 100 W for 10 minutes with simultaneous drying under the regime parameters of the heat carrier t=60 °C, v=3 m/s, d=10 g/kg dry air. makes it possible to reduce wax coating on blueberry berries and to intensify thermal moisture exchange during drying of berries better than using hygrothermal treatment. [ABSTRACT FROM AUTHOR]

Expanding the range of vegetable processing products by increasing the share and diversifying the range of dried vegetables today is expedient and promising. The aim of this study was to determine the best drying option for extending the shelf life of table beet powder using convective, chemoradiation and combined drying methods. The scientific work presents the results of the process of drying beets by convective, chemoradiation, and combined methods. The method of pre-treatment of beets to stabilize the natural color, namely blanching in citric acid with a concentration of 3% when cut into cubes with dimensions of 10 x 10 mm. The kinetics of beet drying was studied by plotting drying curves. The combined (infrared irradiation of raw materials and simultaneous convective heat supply) method of beet drying was chosen, which allows for a reduction in the duration of the process and improves the quality of dried raw materials. The organoleptic and physicochemical parameters of beetroot powder obtained by the combined drying method, which has advantages over convective and chemoradiation drying methods, were studied. The study of the color of beets was carried out after dissolving in water on a KFK-3 photoelectrocalorimeter. To determine the color, an aqueous solution of beetroot powder was used in a ratio of 1: 10. The temperature was 70 0C with a wavelength of 560 nm. In the obtained dried beets, the content of dry substances, the percentage of recovery and the dependence of the regeneration ability on the drying temperature were determined using a refractometer. During the drying of beets, the change in the mass of the raw material (that is, the removal of moisture) was constantly monitored every 5 minutes in order to determine the moisture content in raw materials. Conducted studies established the optimal degree of grinding table beets, which corresponds cutting into 10 x 10 mm cubes, which are pre-treated with citric acid at a concentration of 3%. The results of research on chemoradiation drying made it possible to reduce the drying time and improve the quality of the dried product compared to convective drying, which is confirmed by the drying curves. When the heat carrier temperature increases from 50 to 80 0C, the drying time decreases from 95 to 70 minutes, which is 79% less than with the convective drying method. It was established that with the combined method of drying, the duration of the process is the shortest, and the intensity of the color of the beet particles is close to natural raw materials. The best temperature of the combined method of drying beets was established, which is 70 0C, with a duration of the process of 75 minutes. Organoleptic and physicochemical parameters of the finished product - a powder obtained by the combined drying method, which has advantages over convective and chemoradiation methods - were determined. The change in organoleptic indicators of finished products during storage for 3 months was studied, which indicated excellent storage of beetroot powder. [ABSTRACT FROM AUTHOR]

After being harvested, fresh apples and apricots have a high moisture content and are put through a drying process to reduce waste and lengthen shelf life. This study intends to evaluate the physicochemical parameters during moisture removal and product heating in order to conduct an experimental investigation of the convective drying of apples and apricots in a pilot drying installation. The drying agent's temperature and/or speed can be adjusted using the pilot installation. About the raw materials: the apricots (Neptun variety) were dried and cut into halves, while the apples (Golden Delicious variety) were dried and cut into 4 mm thick slices. The fruits' drying properties were observed at 50 °C, 60 °C, 70 °C, and 80 °C, air speeds of 1.0, 1.5, and 2.0 m/s, and relative air humidity levels of 40–45%. Findings of the ascorbic acid content, color, heating, and dimensional fluctuations are provided and examined. Increased air velocity and temperature had the expected effect of increasing water loss, solid gain, and shrinking. Depending on the drying conditions, different color characteristics were applied. [ABSTRACT FROM AUTHOR]

The seasonal nature of fruits and vegetables has an immense impact on the process of seeking methods that allow extending the shelf life in this category of food. It is observed that through continuous technological changes, it is also possible to notice changes in the methods used to examine and study food and its microbiological aspects. It should be added that a new trend of bioactive ingredient consumption is also on the increase, which translates into numerous attempts that are made to keep the high quality of those products for a longer time. New and modern methods are being sought in this area, where the main aim is to support drying processes and quality control during food processing. This review provides deep insight into the application of artificial intelligence (AI) using a multi-layer perceptron network (MLPN) and other machine learning algorithms to evaluate the effective prediction and classification of the obtained vegetables and fruits during convection as well as spray drying. AI in food drying, especially for entrepreneurs and researchers, can be a huge chance to speed up development, lower production costs, effective quality control and higher production efficiency. Current scientific findings confirm that the selection of appropriate parameters, among others, such as color, shape, texture, sound, initial volume, drying time, air temperature, airflow velocity, area difference, moisture content and final thickness, have an influence on the yield as well as the quality of the obtained dried vegetables and fruits. Moreover, scientific discoveries prove that the technology of drying fruits and vegetables supported by artificial intelligence offers an alternative in process optimization and quality control and, even in an indirect way, can prolong the freshness of food rich in various nutrients. In the future, the main challenge will be the application of artificial intelligence in most production lines in real time in order to control the parameters of the process or control the quality of raw materials obtained in the process of drying. [ABSTRACT FROM AUTHOR]

White mulberry (Morus alba) leaf is highly valued due to its health-promoting attributes. It is specified by a great content of phytochemical constituents with excellent antioxidant properties. This research was conducted at STNanotech Laboratory in 2021 to evaluate the dried tea production from the white mulberry leaf. The total phenolic content, total flavonoid content, DPPH free radical scavenging, FRAP ferric reducing antioxidant and beta-carotene bleaching activity in the raw white mulberry leaf were primarily analyzed. The raw white mulberry leaf was blanched in different conditions (100/5, 95/10, 90/15, 85/20 and 80/25 oC/s) to inactivate enzymes. The blanched leaves were cut into small pieces with dimension of 0.5 × 3.5 cm. The cut mulberry leaves were then convective-dried at different conditions (50/18, 55/15, 60/12, 65/9, and 70/6 oC/h) by a convective dryer. Dried tea was left to cool and ready for testing of total phenolic content, total flavonoid content, DPPH free radical scavenging, FRAP ferric reducing antioxidant and beta-carotene bleaching activity. Results showed that raw mulberry leaves should be blanched in hot water at 95/10 (oC/s) and convective-dried at 60/12 (oC/h) to maintain the highest bioactive contents and antioxidant properties. The dried mulberry leaf tea still retained the most valuable ingredients in raw material. [ABSTRACT FROM AUTHOR]

Onions have a high moisture content, which makes them more susceptible to microbial growth. Drying is one of the postharvest preservation methods applied to decrease onion moisture content, thereby increasing its storage life. In this study, onions were peeled, washed, cut into quarters, hot water blanched, and pureed. The puree was further dried using two different drying methods: refractance window drying (RWD) (water temperature: 70 °C) and convective drying (CD) (50 °C). The puree was spread on prefabricated trays at varying thicknesses of 2 mm, 4 mm, and 6 mm. It was observed that, irrespective of the drying method, moisture ratio (MR) decreased and drying time and effective moisture diffusivity increased with respect to the thickness of the puree. In addition, the Lewis model and the Wang and Singh model showed the highest R2 and lowest SEE value for RWD and CD, respectively. Moreover, the MR of onion puree during RWD and CD was predicted using a multi-layer feed-forward (MLF) artificial neural network (ANN) with a back-propagation algorithm. The result showed that the ANN model with 12 and 18 neurons in the hidden layer could predict the MR, with a high R2 value for RWD and CD, respectively. The results also showed that the thickness of the puree and drying method significantly affected the physicochemical quality (color characteristics, pyruvic acid content, total phenolic content, total flavonoid content, antioxidant capacity, and hygroscopicity) of onion powder. It was concluded that RWD proved to be a better drying method than CD in terms of the quality of dried powder and reduced drying time. Irrespective of the drying method, 2 mm-thick puree dried yielded the best-dried onion powder in terms of physicochemical quality, as well yielding the lowest drying time. These samples were further analyzed for calculating the glass transition temperature. [ABSTRACT FROM AUTHOR]

The present study focused on the effect of different drying temperatures (40, 50, 60 and 70 °C) and combination of pre-treatments: potassium metabisulphite (KMS), potassium metabisulphite + Citric acid + blanching (KCB)] on functional, thermo-pasting and antioxidant properties of elephant foot yam (EFY) powder. Drying temperature and pretreatment reduces the water and oil absorption capacity, and the highest values were 2.34 g/g and 1.19 g/g for drying at 40 °C for the untreated sample, respectively. KMS pretreatment enhanced the bulk density, foaming capacity, emulsion capacity, and emulsion stability with an increase in drying temperature. Pasting temperature and viscosity decreased with an increase in drying temperature, and the maximum was observed at 40 °C for KMS pretreatment. Blanching increases the gelatinization temperature resulting in higher mid-and end-temperatures for KCB pretreatment. The antioxidant properties decreased with an increase in the drying temperature and were found to be minimal in the case of KCB treated samples. [ABSTRACT FROM AUTHOR]

In this investigation, the drying of Stevia rebaudiana leaves was carried out in a lab scale convective hot-air dryer at a varying temperature of 30–80°C to analyze the drying behavior, fit mathematical, Artificial Neural Networks (ANNs), and Adaptive Neuro-Fuzzy System (ANFIS) models to predict the drying kinetics of leaves. Further, dried leaf powders were analyzed for color properties, ascorbic acid and total phenol contents, antioxidant activity, water activity (aw), water solubility index (WSI), hygroscopicity (HG), density (bulk, tapped, and particle), bulk porosity, and flowability indices (Hausner ratio (HR), Carr index (CI), and angle of repose (α)). The results showed that ANFIS model with R2 of 0.9998, offers a more accurate forecast of the drying kinetics of leaves dried in a convective hot-air dryer in comparison to mathematical and ANN modeling. The convective drying significantly (p <.05) effected the L*, a*, b*, hue angle and chroma values of dried leaves. Increase in the drying temperature from 30 to 80°C resulted in a decrement of 50.90% in aw, 10.10% in tapped density, while enhancement of 23.26% in WSI, 32.93% in HG, 54% in particle density, and 10.59% in bulk porosity of dried leaf powder. Notably, ascorbic acid and antioxidant activity decreased with rising temperatures, while total phenols enhanced up to 50°C. The bulk density of dried samples remained largely unchanged with increasing temperature, while the flowability of the Stevia powder improved. Thus, these findings provide valuable insights for producers regarding the drying characteristics and properties of Stevia leaf powder. [ABSTRACT FROM AUTHOR]

The popularity of edible flowers is increasing day by day and new solutions are sought due to their short shelf life. For this purpose, in this study, four different colors of Viola × wittrockiana Gams.; white (Fino Clear White), orange (Delta Pure Orange), bordeaux/mauve rose (Mammoth Rocky Rose), and yellow (Delta Premium Pure Lemon) flowers were dried at drying air temperature of 60, 70, and 80 °C with a convective hot air dryer. Color (L*, a*, b*, C*, h°, ∆E, and BI), drying time and bioactive compounds (Total Phenolic Content (TPC), anthocyanin content (AC), and antioxidant activity (AO) values were measured). The orange flowers showed the fastest drying (78 min at 80 °C). The lowest total color change (∆E) (4.58 at 70 °C) and browning index (BI) (9.58 at 60 °C) values were observed in all drying processes of white flowers. The highest AC was determined in bordeaux flowers in both fresh (2.4 mg malvidin glucoside/g) and dried (25.57 mg malvidin glucoside/g at 60 °C) samples. The AO decreased in all samples depending on the temperature increase, it was found that the most beneficial result in terms of bioactive compounds was the bordeaux flowers dried at drying air temperature of 60 °C. [ABSTRACT FROM AUTHOR]

Machine learning and mathematical modeling techniques have been conducted to model the thin layer drying kinetics of pea pods, under either microwave or conventional air drying,. The effect of nine different microwave output powers (200–1000 W) and five different ventilated oven temperatures (40, 60, 80, 100, and 120°C) on drying kinetics was studied. The experimental drying rates were fitted to 11 literature semi‐empirical models to determine the kinetic parameters, finding the higher goodness‐of‐fit for the Midilli et al. model (average R2 = 0.999 for both drying methods). Moreover, the data were modeled using support vector machine (SVM) for regression which was optimized with dragonfly algorithm (DA) technique. The best result was obtained by Gaussian kernel with the optimal parameters σ, C, and ε values estimated as 0.2871, 78.45, and 0, respectively. The small root mean square error (RMSE = 0.0132) and the high determination coefficient (R2 = 0.9983) values proved how robust the SVM model is. DA‐SVM techniques can reliably be utilized to describe the thin layer drying kinetics of pea pods. It is useful to provide models that can assist in the development of food process control algorithms, and provided insights into complex processes, for the technological design of microwave or convective drying for pea pods preservation. Practical applications: Drying of by‐products from pea processing industry was investigated as a critical step prior to their valorization. The drying of pea pods has never been investigated before which is the case of the present study whose objective was to study and model the microwave and convective drying kinetics of pea pods. Our research work reported that the Midilli et al. model was the most appropriate to describe the thin layer drying kinetics of pea pods for both drying methods, but mathematical drying models, although a useful tool, remains empirical in nature and product specific. Because of these limitations the new model DA‐SVM, developed using artificial intelligence techniques, can reliably be used to describe the nonlinear behavior of pea pods drying. These results could be further used for scale up calculation, which would further allow industrial scale preservation by microwave or convective drying of pea pods. [ABSTRACT FROM AUTHOR]

The present study focuses on the effect of different drying temperatures (DT) (40, 60 and 80°C) and the combination of banana slice thicknesses (BST) (2 and 4 mm) on the physicochemical properties and phytochemicals of green banana flour (GBF). The influence of the drying temperature and thickness of the banana pulp slice were significant (p

This study explores the unexploited potential of Artificial Neural Network (ANN) optimization techniques in enhancing different drying methods and their influence on the characteristics of various sweet potato varieties. Focusing on the intricate interplay between drying methods and the unique characteristics of white, pink, orange, and purple sweet potatoes, the presented experimental study indicates the impact of ANN-driven optimization on food-related characteristics such as color, phenols content, biological activities (antioxidant, antimicrobial, anti-hyperglycemic, and anti-inflammatory), chemical, and mineral contents. The results unveil significant variations in drying method efficacy across different sweet potato types, underscoring the need for tailored optimization strategies. Specifically, purple sweet potatoes emerge as robust carriers of phenolic compounds, showcasing superior antioxidant activities. Furthermore, this study reveals the optimized parameters of dried sweet potato, such as total phenols content of 1677.76 mg/100 g and anti-inflammatory activity of 8.93%, anti-hyperglycemic activity of 24.42%. The upgraded antioxidant capability is presented through DPPH●, ABTS●+, RP, and SoA assays with values of 1500.56, 10,083.37, 3130.81, and 22,753.97 μg TE/100 g, respectively. Additionally, the moisture content in the lyophilized sample reached a minimum of 2.97%, holding favorable chemical and mineral contents. The utilization of ANN optimization proves instrumental in interpreting complex interactions and unlocking efficiencies in sweet potato drying processes, thereby contributing valuable insights to food science and technology.

Tisane is a fruit or herbal infusion, commonly referred to as herbal tea. These products are consumed as part of a balanced diet, which is closely related to the trend of a healthier lifestyle. In this work, tisanes prepared from rosehip (R), and herbal mixtures containing rosehip/hibiscus flowers (R/H) and rosehip/hibiscus flowers/saffron (R/H/S) were studied. Rosehip was dried by the convective drying method at 40, 50 and 60 °C. Total phenolic content (TPC), total flavonoid content (TFC), total flavonol content (TFlC), total anthocyanin content (TAC), antioxidant properties (DPPH∙ and ABTS∙+ assays) and in vitro inhibitory potential toward α-amylase of tisanes were examined. The highest TPC (based on dry weight (dw)) was measured in tisane obtained from rosehip dried at 60 °C (37.84 mg GAE/g dw). Tisanes prepared from a R/H/S mixture had the highest values of TFC (4.66–6.13 mg QUE/g dw), TFlC (2.67–3.98 mg QUE/g dw) and TAC (1.35–2.27 mg Cy 3-glc/g dw). The highest DPPH∙ scavenging activity (53.42 mg TE/g dw) was measured in rosehip (dried at 60 °C) tisane, whereas tisane prepared from a rosehip (dried at 60 °C)/hibiscus mixture expressed the best ABTS∙+ scavenging activity (107.44 mg TE/g dw). All tisane samples expressed high inhibitory potential toward α-amylase, with the highest activity of 85.03% and 89.90%, measured for tisanes prepared from rosehip/hibiscus flowers mixture (rosehip dried at 50 and 60 °C, respectively).

This work reports the results obtained with an innovative configuration of a closed-static solar greenhouse for sludge drying. The novelty of the solar greenhouse configuration consisted in using a forced ventilation system to provide hot air for sludge drying and the utilization of solar irradiation for energy supply. Wet sewage sludge (97% humidity) was successfully dried up to a residual humidity close to 5% after 25 days during wintertime. The increase of the airflow rate supplied under the sludge bed improved the sludge drying rate. Moreover, the fraction of volatile suspended solids decreased from 70% to 41% after 13 days, indicating that air supply promoted the simultaneous stabilization of the sludge as a side-effect to the drying process. Overall, the specific energy consumption per ton of evaporated water was estimated to approximately 450 kWh/t, resulting in about 55% of energy demand lower than a conventional thermal drying system, while using only free solar energy. The achieved high weight reduction of up to 99% implies a noticeable reduction of the excess sludge handling costs, indicating that solar greenhouse drying is a highly interesting opportunity for sludge drying in medium-small sized WWTPs.

Ceramic filter elements (FE) based on aluminosilicate fibers are produced by vacuum forming, using various drying methods. Microwave drying and freezing followed by drying are used as methods to reduce binder migration. FE microstructure, tensile strength, and aerodynamic resistance are analyzed. The characteristics obtained are compared with FE prepared using convective drying. [ABSTRACT FROM AUTHOR]

As a section on improving the energy efficiency and thermal efficiency of convection dryers, a different airflow distribution system in the convection dryer was established. The grape drying experiment was investigated by applying three types of distribution air inside a convection hot-air dryer. The vertical system (VS) in which hot air passes vertically through the tray of samples. However, the air was delivered parallel to the sample tray in two horizontal systems (HS) Types (I, II). The investigations were approved with the different air-drying temperatures of 40, 50, and 60 °C at different velocity 1.0, 1.5, and 2.0 m/s. The drying time in the horizontal dryer compared to the vertical system was significantly less. The data analysis showed that horizontal energy consumption with a type (II) dryer was low while the energy consumption was high under the vertical dryer. Moreover, applying the horizontal Type (II) for grapes drying had numerous improvements above the conventional vertical system, such as shorter processing times, less overall energy utilisation, and higher dryer thermal efficiency. According to the results, after fitting the experimental data with eleven drying kinetics models and comparing the results in terms of the root mean square error (RMSE), the reduced chi-square (χ2), and the correlation coefficient (R2), it was obtained that logarithmic model can give practically accurate evaluations of the drying curve for grapes drying in different convection dryers. [ABSTRACT FROM AUTHOR]

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Air-drying kinetics of potato peel, a wastage of potato processing, was characterized in this work. For this, potato peel samples were dried in convective dryer at different operating conditions from which drying kinetics curves were estimated. Potato flesh samples were dried under the same conditions for comparison purposes. As well, proximate composition, scanning electron microscopy images of tissue structure, total phenolics and chlorogenic acid contents, were determined to characterize fresh and dried samples of potato peel and flesh. Sorption isotherms at ambient temperature were also established. Both drying kinetics curves and sorption isotherms were well fitted by Fick's and Guggenheim–Anderson-de Boer mathematical models. Results pointed out the need for appropriate selection of drying parameters in further transformation of potato waste. [ABSTRACT FROM AUTHOR]

Foods shrink and deform when air-dried; thus, these phenomena have been included in drying models as they affect the estimated both moisture behavior and water diffusivities (D ). However, these models are not used to estimate the morphometric parameters of dried foods, especially shape indices, as they are almost exclusively described by experimentally data-driven empirical equations. Therefore, this study was aimed at obtaining several morphometric indices from the solution of a drying model incorporating both the size and shape changes of foods. The model was used to analyze drying data of a non-cellular model food (mortadella slices, 9.5 mm × 9.5 mm × 80 mm) obtained at 60, 70 and 80 °C, where its morphometric behavior was monitored by image analysis. When solved, the drying model reproduces the shape changes of food occurring between its initial and final states, allowing the estimation of morphometric parameters such as the available surface for mass transfer (S ), the specific area (a ), the compactness (c ), and the roundness (r ), this last property evaluated trough a previously unreported algorithm. The food-deforming drying model reproduced the evolution of all the morphometric parameters with a low error ( M R D < 8 % ). The drying model was unable to reproduce the shape indices (c and r ) when deformation was not considered in the solution, while S and a separated from the experimental trend at free moisture fractions < 0.5. D values estimated with food deformation were between 1.21 × 10−10 and 1.95 × 10−10 m2/s, while about a 9% overestimation of this property occurred when this phenomenon was neglected. [ABSTRACT FROM AUTHOR]

The drying industry has grown considerably due to the tremendous demand for non-perishable food. Convective drying is one of the most popular equipment in the drying industry (food, chemical, pharmaceutical, etc.). One of the drawbacks of this equipment, when used for convective drying, is the non-uniformity in the final product quality. This study presents the development of a numerical model through Computational Fluid Dynamics (CFD). The drying chamber of a heat pump dryer is assessed from the perspective of drying air velocity and temperature profiles. The model was developed by solving different transport phenomena-related equations. The established methodology was set up to evaluate how the drying air velocity and temperature distribution affect the drying chamber. These results will define if there is a need to redesign it. The air velocity and temperature profile results show a need to redesign the chamber. Only trays 2, 3, and 4 are the ones that would achieve the drying of the products. The proposed solution is to implement air distributors or modify the tray positioning to make the drying air and temperature distribution homogeneous. [ABSTRACT FROM AUTHOR]

Summary: Drying is a popular food preservation technology that reduces food waste and promotes food preservation and food security. Though drying reduces microbial growth and increases shelf life of fruits, it alters sensory properties both favourably and unfavourably depending on the nature of the drying process applied and significantly influences the final product quality. However, there is currently no review article on the impact of the drying process on the sensorial quality attributes of tropical fruits. This review attempts to describe the relative merits and challenges of some widely used advanced drying techniques with a particular focus on intermittent microwave convective drying (IMCD) techniques which offer high sensory properties with excellent drying efficiency. The paper aims to provide an insight into the effect of these drying techniques on the sensory qualities of tropical fruits to identify the best drying method for future food applications. [ABSTRACT FROM AUTHOR]

Various methods of drying spicy-aromatic raw materials are described. The kinetic laws governing the process of convective drying of the ginger and galangal roots have been established. The stadial regimes of dehydration, in accordance with which the temperature of the drying agent in the first stage of the process is maintained at a level of 60°C and in the second at 45°C are substantiated and developed scientifically. The established regimes make it possible to reduce the expenditures of heat in drying and ensure the most complete preservation of the natural components of the starting material. A mathematical model of heat and mass transfer, phase transformations, and shrinkage is proposed, which can be used to establish dehydration regimes. The calculation of the total duration of the process of drying by V. V. Krasnikov's method is presented. [ABSTRACT FROM AUTHOR]

Based on the zonal method, the temperature and concentration dependences of the moisture diffusion coefficient in materials subject to shrinkage in the process of drying (plates cut from apple, carrot, and beet) were found experimentally. The concentration dependences of the moisture diffusion coefficient in these materials were determined from drying curves obtained in the absence of external diffusion resistance. Shrinkage of materials was determined experimentally, the temperature dependences of the obtained diffusion coefficients were described on the basis of the theory of activated molecular diffusion of moisture in the material. It is shown that the temperature dependence of the moisture diffusion coefficient in the indicated materials is described satisfactorily by the Arrhenius equation, on the basis of which, for these materials, formulas were obtained that express the dependence of the coefficient of moisture diffusion in them on their moisture content and temperature and that can be used in engineering calculations. The obtained data on the moisture diffusion coefficient in the studied materials are compared with similar data obtained for other materials. It is shown that the concentration dependences of the moisture diffusion coefficients of materials subject to shrinkage during drying have the same nature and order of magnitude as similar dependences for materials without shrinkage. The drying curves calculated using the obtained formulas were compared with the experimental drying curves, which showed their satisfactory similarity. [ABSTRACT FROM AUTHOR]

This paper presents the results of research on the influence of selected drying methods and parameters on the physicochemical properties of tomatoes. The samples were subjected to the process of convection and vacuum drying at the temperature of 60 and 80 °C for 2 and 4 h, and then their physical properties (colour, weight loss, water activity, dry matter content) and chemical properties (extract content, total acidity, total antioxidant activity, vitamin C, lycopene, total phenols, flavonoids and their losses during drying) were compared with a control sample. Both drying method, temperature and time had a significant effect on colour of the tomatoes after drying. Lightness for convective drying for 4 h was significantly lower at 80 °C compared with 60 °C (32.21 and 36.58 respectively). The smallest content of ascorbic acid was recorded for samples dried under convection conditions for 4 h at 80 °C (5.68 mg). In addition, the amount of lycopene dropped drastically for samples dried under vacuum and convection for 4 h at 80 °C (1.51 and 1.10 mg respectively). On the basis of the obtained results, it was found that a properly conducted drying process and well-chosen temperature and time parameters contribute to the reduction of antioxidant losses as well as colour changes of the final product. It is recommended to dry tomato samples at a temperature no higher than 60 °C in vacuum to avoid browning reactions which influence on the colour of the tomatoes, as well as high losses of antioxidants. [ABSTRACT FROM AUTHOR]

Solar collectors are thermal devices that can trap solar energy and convert it to heat. This heat can be used for different industrial applications, for example, the drying of food is one of the most useful applications of solar collectors. This work aims to design and build a solar collector using nanofluids for the convective drying of food. The dimensions of the solar collector were 1 m² by 20 cm with an angle of inclination of 45°. The collector was composed of 9-mm thick tempered glass and a heat exchanger in which the nanofluids circulate. Nanofluids were designed based on canola oil and nanopowders (>50 nm) of Al2O3, CuO, and a 1:1 (w/w) mixture of both. Thermal profiles were determined using differential scanning calorimetry (DSC). The solar collector temperatures were recorded using an Agricos® unit. The maximum temperatures of the air leaving the collector were 39.1°C, 44°C, 54°C, and 47.1°C for canola oil, and the nanofluids composed of Al2O3, CuO, and the 1:1 mixture, respectively, with a maximum efficiency of 65.09%. An increase in the outlet air temperature was observed using the nanofluids compared to canola oil alone [ABSTRACT FROM AUTHOR]

This study aimed to optimize the convective drying of blueberry pomace (BP) to enhance fiber functionality and bioactive compound retention. BP was dried at 50−90 °C with an airflow of 2.5 m s−1. Drying kinetics were modeled using five mathematical models, with the Page model showing the highest accuracy (R 2 = 0.9965−0.9996). Higher temperatures increased drying rates (3.7 × 10−3 to 1.2 × 10−2 kg H 2 O kg−1 db min−1) and moisture diffusivity (4.00 × 10−8 to 2.17 × 10−7 m2 s−1), with an activation energy of 39.55 kJ mol−1. Total dietary fiber remained stable (20.85 ± 0.17 g 100 g−1 db), while soluble fiber increased (3.11–4.66 g 100 g−1 db) with temperature. Water- and oil-holding capacities decreased (10.86–8.61 mL g−1 db and 3.85 to 3.44 mL g−1 db, respectively). The highest total phenolic content (13.65 ± 0.12 mg GAE g−1 db) and antioxidant activity (6.65 mg AAE g−1 db for DPPH) were observed at 70 °C. Energy consumption decreased significantly (13.88–6.95 kW h−1), leading to reduced CO 2 emissions. This study demonstrates the effective use of the Page model to optimize convective drying at 70 °C, reducing production costs by 47% and highlighting its potential to produce fiber-rich ingredients from BP with enhanced techno-functional and bioactive properties. [Display omitted] • Higher temperatures enhance the drying efficiency of blueberry pomace. • Page model best predicts drying; activation energy of 39.55 kJ mol−1. • Above 70 °C, soluble fiber increases while insoluble decreases. • Techno-functional properties are modified by increasing temperatures. • Bioactive compounds and antioxidant activity increase with higher temperatures. [ABSTRACT FROM AUTHOR]

Electrohydrodynamic (EHD) drying relies on the generation of a corona wind that is created with a high electric potential between an emitter and a ground electrode. The impinging corona wind enhances convective heat and mass transport close to the sample, which is positioned on the ground electrode. Although EHD drying is reported to have large potential for milder and energy efficient drying, most studies have only evaluated its potential at the lab scale and for specific applications. This review focusses on discussing the underlying physical phenomena that may be expected to influence the performance of EHD drying processes. Specifically, we discuss how corona wind changes due to discharge behaviour as it is influenced by moisture release during drying, how the microstructural properties of the product could influence electromigration in the drying material and how EHD drying could be efficiently and safely scaled up for biobased & food products. We conclude with an outlook to the research that still is required to concretize the potential of EHD drying in practice. In EHD drying, electrical discharge induces airflow which enhances external convective drying. Studies coupling physical phenomena are still lacking, although some possible couplings are mentioned in chapter 2. Internal mass transfer is enhanced due to presence of an electrical potential over the product, which can cause several electrically-driven transport phenomena a s discussed in chapter 3. Several drying setups have been explored in industry, of which the characteristics are summarized in chapter 4. • In EHD drying, moisture transport is enhanced using electrical phenomena. • Phenomena occurring in the air domain and interactions between them are summarized. • Suggestions are made for electrically driven internal moisture transport phenomena. • Current EHD setups and the (dis)advantages of their characteristics are discussed. [ABSTRACT FROM AUTHOR]

Convective thermal drying is usually used in sludge dryers, and the air supply forms significantly affect the sludge drying efficiency. In this work, the drying process of multi-layered sludge is numerically simulated using a coupled computational fluid dynamics-discrete element method (CFD-DEM) approach. Better than our previous work, the current CFD-DEM model further considers the dynamic process of humidity within the flow field. Firstly, the CFD-DEM model is validated based on the mechanistic experimental data. Then, extensive numerical simulations are carried out to investigate the two-layered sludge drying process in the dryer, and the effects of two conventional air supply forms (Top-to-Bottom and Bottom-to-Top) as well as a novel air supply form (Side-assist) on the two-phase flow system are discussed. The simulation results provide in detail the dynamic processes of momentum, heat and mass (moisture) in the convective drying system under different working conditions. Following recommendations are presented to facilitate the operation of the dryer: Bottom-to-Top is better for sludge drying and tends to utilize less heat from the heat source compared to the Top-to-Bottom. The drying efficiency can be further improved by supplying the Side-assist with an optimal flow ratio of side-wind to bottom-wind. Numerical results show that the optimal flow ratio is related to the total air volume, the deflection angle and the side-wind temperature. The present study reveals in depth the impact mechanism of the air supply form on the convective thermal drying process of sludge, which contributes to the design and optimization of high-efficiency dryers. [Display omitted] • A CFD-DEM model describing the sludge drying process is further developed. • The convective drying of multi-layered sludge is numerically investigated. • Two conventional air supply forms for the dryer are analyzed. • A novel air supply form and its optimal solution are proposed. [ABSTRACT FROM AUTHOR]

Melon is a dessert loved by many, captivating with its thick aroma and delicate honey taste. The juicy, fragrant pulp is not only delicious but also very useful for dietary purposes, with a therapeutic effect on diseases of the liver and kidneys, anaemia, rheumatism and cardiovascular disorders. This storehouse of vitamins is especially rich in potassium and iron salts, pectins, fibre, easily digestible sugars, proteins, starch and other elements necessary for health. This article presents the results of a study of the Myrzachulskaya melon variety and establishes the optimal parameters for drying the pulp, pre-treating melons with 99.5% ethanol before drying. Twenty drying experiments were carried out, in which the parameters of the operating variables, namely temperature, air velocity and sample size, were varied according to the compiled mathematical processing planning matrix. Drying caused a decrease in biologically active compounds, affecting some antioxidant properties (vitamin C content, total phenol content and antioxidant capacity) of melon pulp. As a result, the optimal parameters were established, at which samples of dried melon pulp showed insignificant losses (up to 1%) in the total content of phenolic compounds, carotenoids and ascorbic acid. The optimal parameters for drying melon fruits are a temperature of 55 °C, a drying time of 11 h and a slice thickness of not more than 0.5 cm.

The influence of drying process on the properties of ceramic filter elements for industrial high-temperature gases purification was studied. Filter elements were based on aluminosilicate fiber manufactured via vacuum filtration with the following molding and machining of the workpiece, it's treatment with a colloidal silicon oxide sol binder, and drying with the employment of various processes. Convective drying (CD), microwave drying (MWD) and filter element freezing followed by convective drying (FCD) processes were employed to study the related binder migration and its effect on filter properties. Diffusional redistribution of the binder through the thickness of the filter element's wall decreases in the series CD→FCD→MWD with the accordingly observed improvement of the structural uniformity and mechanical strength of the filters. The tensile strength of samples dehydrated via convective drying, freezing followed by convective drying and microwave drying, all of which then heat-treated at 1000 °C (the assumed maximum operating temperature), is 0.35 MPa, 0.57 MPa and 0.48 MPa, respectively. The pressure drop measured at the specific air flow of 100 m3/m2 is respectively 700Pa, 490Pa and 410Pa. [ABSTRACT FROM AUTHOR]